Pipe inner surface measuring method and apparatus

Abstract

Light is introduced to an inner surface of a fine tube, which is an object for measurement of the inner surface roughness, through a first end of the fine tube at a small angle with respect to a center line of the fine tube and the light emerging from a second end of the fine tube after the light is reflected by multiple reflections within the fine tube is measured to evaluate the roughness of the inner surface of the fine tube. Upon such measurement, the light to be introduced to the first end of the fine tube is converged once on the center line of the fine tube and then diverged again, and the polarization direction of the light to be introduced to the first end of the fine tube is set to an angle equal to or around 90 degrees with respect to the reflection surface of the fine tube. Thus, the roughness of the inner surface of the fine tube can be calculated in accordance with a result of detection of the intensity of emergent light from the fine tube by means of a photo detector.

What is claimed is: 
     
       1. An apparatus for measuring the roughness of the inner surface of a tube, comprising: a holding mechanism for holding a tube having an inner surface whose roughness is to be measured; polarization means for polarizing light from a light source in a polarizing direction;   an incident optics system positioned for converging light from the light source on the center line of the tube and then introducing the light into the tube at an incident angle with respect to the center line such that the light is reflected multiple times from an inner surface of the tube, wherein a direction of polarization of the polarized light is about 90° with respect to the inner surface of the tube from which the polarized light reflects;   a photo detector for receiving light emerging from a second end of the tube and outputting an electric signal corresponding the intensity of the light; and   signal processing means for calculating the roughness of the inner surface of the tube in accordance with the electric signal output from said photo detector.   
     
     
       2. An apparatus for measuring the roughness of the inner surface of the tube according to claim 1, wherein said incident optics system includes an optical axis adjustment mechanism for adjusting the optical axis of the light from said light source so that the converging point of the light coincides with the center line of the tube. 
     
     
       3. An apparatus for measuring the roughness of the inner surface of the tube according to claim 1, further comprising a movable table for movably holding said entire incident optics system thereon, the optical axis of the light from said light source being adjusted by adjusting the position of said movable table. 
     
     
       4. An apparatus for measuring the roughness of the inner surface of the tube according to claim 1, wherein said holding mechanism includes a mechanism for rotating the tube around the axis of the same. 
     
     
       5. An apparatus for measuring the roughness of the inner surface of the tube according to claim 1 further comprising: a receiving optics system from converging light emerging from the second end of the tube at a predetermined convergence position;   wherein said photo detector is disposed at the convergence position of the emergent light for measuring the intensity of light at a central portion of the convergent light and the intensity of light at a peripheral portion of the convergent light separately from each other; and   wherein said signal processing means comprises means for calculating the roughness of the inner surface of the tube in accordance with the ratio between the intensity of light at the central portion of the convergent light and the intensity of light at the peripheral portion of the convergent light measured by said photo detector.   
     
     
       6. A method of measuring the roughness of an inner surface of a tube, comprising the steps of: introducing light into the tube from a first end thereof, said introducing step comprising converging polarized light on the center line of the tube such that the light diverges from the center line, and applying the diverging light onto the inner surface of the tube at such an angle relative to the tube axis that the applied light is reflected multiple times from the inner surface of the tube and emerges from a second end of the tube; and   evaluating the surface roughness of the inner surface of the tube based upon an intensity characteristic of the light emerging from the second end of the tube,   wherein a direction of polarization of the polarized light is about 90° with respect to the inner surface of the tube from which the polarized light reflects.   
     
     
       7. A method of measuring the roughness of an inner surface of the tube according to claim 6 wherein said step of evaluating the surface roughness comprises: measuring the intensity of light of specular reflection components and the intensity of light of diffuse scattering components of the light emerging from a second end of the tube; and   measuring the roughness of the inner surface of the tube in accordance with the ratio between the intensity of light of the specular reflection components and the intensity of light of the diffuse scattering components.   
     
     
       8. A method of measuring the roughness of the inner surface of the tube according to claim 7, wherein the light emerging from the tube is converged, and the intensity of light at a central portion of the converged light and the intensity of light at a peripheral portion of the converted light are measured separately from each other to measure the intensity of light of the specular reflection components and the intensity of light of the diffuse scattering components.